############################################################################
# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
#
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.
#
# See the COPYRIGHT file distributed with this work for additional
# information regarding copyright ownership.
############################################################################

import re

# Helper functions and variables

def added_lines(target_branch, paths):
    import subprocess
    subprocess.check_output(['/usr/bin/git', 'fetch', '--depth', '1', 'origin',
                             target_branch])
    diff = subprocess.check_output(['/usr/bin/git', 'diff', 'FETCH_HEAD..',
                                    '--'] + paths)
    added_lines = []
    for line in diff.splitlines():
        if line.startswith(b'+') and not line.startswith(b'+++'):
            added_lines.append(line)
    return added_lines

issue_or_mr_id_regex = re.compile(br'\[(GL [#!]|RT #)[0-9]+\]')
release_notes_regex = re.compile(r'doc/(arm|notes)/notes-.*\.(rst|xml)')

modified_files = danger.git.modified_files
mr_labels = danger.gitlab.mr.labels
target_branch = danger.gitlab.mr.target_branch

###############################################################################
# COMMIT MESSAGES
###############################################################################
#
# - FAIL if any of the following is true for any commit on the MR branch:
#
#     * The subject line starts with "fixup!" or "Apply suggestion".
#
#     * There is no empty line between the subject line and the log message.
#
# - WARN if any of the following is true for any commit on the MR branch:
#
#     * The length of the subject line exceeds 72 characters.
#
#     * There is no log message present (i.e. commit only has a subject) and the
#       subject line does not contain any of the following strings: "fixup! ",
#       " CHANGES ", " release note".
#
#     * Any line of the log message is longer than 72 characters.  This rule is
#       not evaluated for lines starting with four spaces, which allows long
#       lines to be included in the commit log message by prefixing them with
#       four spaces (useful for pasting compiler warnings, static analyzer
#       messages, log lines, etc.)

for commit in danger.git.commits:
    message_lines = commit.message.splitlines()
    subject = message_lines[0]
    if subject.startswith('fixup!') or subject.startswith('Apply suggestion'):
        fail('Fixup commits are still present in this merge request. '
             'Please squash them before merging.')
    if len(subject) > 72:
        warn(
            f'Subject line for commit {commit.sha} is too long: '
            f'```{subject}``` ({len(subject)} > 72 characters).'
        )
    if len(message_lines) > 1 and message_lines[1]:
        fail(f'No empty line after subject for commit {commit.sha}.')
    if (len(message_lines) < 3 and
            'fixup! ' not in subject and
            ' CHANGES ' not in subject and
            ' release note' not in subject):
        warn(f'Please write a log message for commit {commit.sha}.')
    for line in message_lines[2:]:
        if len(line) > 72 and not line.startswith('    '):
            warn(
                f'Line too long in log message for commit {commit.sha}: '
                f'```{line}``` ({len(line)} > 72 characters).'
            )

###############################################################################
# MILESTONE
###############################################################################
#
# FAIL if the merge request is not assigned to any milestone.

if not danger.gitlab.mr.milestone:
    fail('Please assign this merge request to a milestone.')

###############################################################################
# VERSION LABELS
###############################################################################
#
# FAIL if any of the following is true for the merge request:
#
# * The "Backport" label is set and the number of version labels set is
#   different than 1.  (For backports, the version label is used for indicating
#   its target branch.  This is a rather ugly attempt to address a UI
#   deficiency - the target branch for each MR is not visible on milestone
#   dashboards.)
#
# * Neither the "Backport" label nor any version label is set.  (If the merge
#   request is not a backport, version labels are used for indicating
#   backporting preferences.)

backport_label_set = 'Backport' in mr_labels
version_labels = [l for l in mr_labels if l.startswith('v9.')]
if backport_label_set and len(version_labels) != 1:
    fail('The *Backport* label is set for this merge request. '
         'Please also set exactly one version label (*v9.x*).')
if not backport_label_set and not version_labels:
    fail('If this merge request is a backport, set the *Backport* label and '
         'a single version label (*v9.x*) indicating the target branch. '
         'If not, set version labels for all targeted backport branches.')

###############################################################################
# OTHER LABELS
###############################################################################
#
# WARN if any of the following is true for the merge request:
#
# * The "Review" label is not set.  (It may be intentional, but rarely is.)
#
# * The "Review" label is set, but the "LGTM" label is not set.  (This aims to
#   remind developers about the need to set the latter on merge requests which
#   passed review.)

if 'Review' not in mr_labels:
    warn('This merge request does not have the *Review* label set. '
         'Please set it if you would like the merge request to be reviewed.')
elif 'LGTM (Merge OK)' not in mr_labels:
    warn('This merge request is currently in review. '
         'It should not be merged until it is marked with the *LGTM* label.')

###############################################################################
# 'CHANGES' FILE
###############################################################################
#
# FAIL if any of the following is true:
#
# * The merge request does not update the CHANGES file, but it does not have
#   the "No CHANGES" label set.  (This attempts to ensure that the author of
#   the MR did not forget about adding a CHANGES entry.)
#
# * The merge request updates the CHANGES file, but it has the "No CHANGES"
#   label set.  (This attempts to ensure the the "No CHANGES" label is used in
#   a sane way.)
#
# * The merge request adds a new CHANGES entry that does not contain any
#   GitLab/RT issue/MR identifiers.

changes_modified = 'CHANGES' in modified_files
no_changes_label_set = 'No CHANGES' in mr_labels
if not changes_modified and not no_changes_label_set:
    fail('This merge request does not modify `CHANGES`. '
         'Add a `CHANGES` entry or set the *No CHANGES* label.')
if changes_modified and no_changes_label_set:
    fail('This merge request modifies `CHANGES`. '
         'Revert `CHANGES` modifications or unset the *No Changes* label.')

changes_added_lines = added_lines(target_branch, ['CHANGES'])
identifiers_found = filter(issue_or_mr_id_regex.search, changes_added_lines)
if changes_added_lines and not any(identifiers_found):
    fail('No valid issue/MR identifiers found in added `CHANGES` entries.')

###############################################################################
# RELEASE NOTES
###############################################################################
#
# - FAIL if any of the following is true:
#
#     * The merge request does not update release notes and has the "Release
#       Notes" label set.  (This attempts to point out missing release notes.)
#
#     * The merge request updates release notes but does not have the "Release
#       Notes" label set.  (This ensures that merge requests updating release
#       notes can be easily found using the "Release Notes" label.)
#
# - WARN if this merge request updates release notes, but no GitLab/RT issue/MR
#   identifiers are found in the lines added to the release notes by this MR.

release_notes_regex = re.compile(r'doc/(arm|notes)/notes-.*\.(rst|xml)')
release_notes_changed = list(filter(release_notes_regex.match, modified_files))
release_notes_label_set = 'Release Notes' in mr_labels
if not release_notes_changed and release_notes_label_set:
    fail('This merge request has the *Release Notes* label set. '
         'Add a release note or unset the *Release Notes* label.')
if release_notes_changed and not release_notes_label_set:
    fail('This merge request modifies release notes. '
         'Revert release note modifications or set the *Release Notes* label.')

if release_notes_changed:
    notes_added_lines = added_lines(target_branch, release_notes_changed)
    identifiers_found = filter(issue_or_mr_id_regex.search, notes_added_lines)
    if notes_added_lines and not any(identifiers_found):
        warn('No valid issue/MR identifiers found in added release notes.')